Pulverized coal feeding apparatus for furnaces



Jan. 7, 1941.

W. 5. ROGERS PULVERIZED COAL FEEDING APPARATUS FOR FURNACES Filed Aug. 2, 1939 3 Sheets-Sheet l Jan. 7, 1941. w. B. ROGERS 2 I PULVERIZED COAL FEEDING APPARATUS FOR FURNACES Filed Aug. 2, 1939 3 Sheets-Sheet 2 7.? 3?? 1L r i Jan. 7, 1941. w. B. ROGERS PULVERIZED COAL FEEDING APPARATUS FOR FURNACES Filed Aug. 2, 1939 3 Sheets-Sheet 3 Patented Jan. 57, 19 41 UNITED STATES PATENT OFFICE PULVERIZED COAL FEEDING APPARATUS FOR FURNACES William B. Rogers, Baltimore, Md.

Application August 2, 1939, Serial No. 288,016

9 Claims.

This invention is a novel pulverized fuel feeding apparatus for delivering powdered coal or the like suspended in air or gas into a burner, said apparatus being particularly adapted for domespractical embodiment thereof to enable others familiar with the art to adopt and use the same; and will summarize in the claims, the novel features of construction, and novel combinations of parts, for which protection is desired.

In said drawings:

Fig. 1 is a transverse section through the apparatus on the line l--l, Fig. 2.

Fig. 2 is a horizontal section through the apparatus on the line 2-2, Fig. 1.

Fig. 3 is a longitudinal section on the line 3-3, Fig. 2; and

Fig. 4 is an end view showing the driving means of the apparatus.

As shown, the apparatus is mounted'in a skeleton frame having a rectangular base I, and uprights 3 at the corners thereof connected by top bars 4 to form a rigid structure. A hopper is suspended within the frame coextensive with the area of the top thereof, said hopper being contracted at its lower end towards one side of the frame, said hopper being provided with end plates 5, and side plates 1 converging at angles of approximately 27 from the vertical to meet the rounded lowerend 6 of the hopper. The side plates 1 of the hopper are suspended at their upper ends on the top bars 4 of the frame, and are adapted to be jolted or shaken as hereinafter described to insure properand even feeding of the powdered fuel down into bottom 6 of the hopper.

From one end of bottom 6 of the hopper extends a tubular casting 2; and journaled in a bearing block 2a in the outer end of casting 2 and in a bearing a (Fig. 2) in the opposite end plate 5 of the hopper is a shaft '8 carrying a conveyor screw 9 adapted to move the powdered fuel from the bottom of the hopper through the casting 2, bearing block 2a in casting 2 being located beyond the outer end of screw 9.

The main function of the apparatus is to feed the properamount of powdered coal as evenly as possible into the proper volume of air, and to (Cl. sot-17) mix the two as thoroughly as possible before delivery thereof through the outlet duct of the apparatus into the burner attachment of the furnace. I have found that the major problem en countered in firing pulverized or finely divided coal, or other solid fuel, in small combustion chambers is to maintain an essentially smooth or even flow of coal and air into the combustion chamber so that the coal will be mixed perfectly with the primary air delivered by the fan or 10 blower. In order to insure that the coal fed by screw 9 will be at an even rate, regardless of whether the hopper 5+! is full of powdered coal or is nearly empty, I have devised a novel hopper agitator which will not only vibrate the coal directly over the screw 9 to create a uniform flufiiness in the mass of coal at this point, but

"mentioned functions of the agitators the most important, by far, is the conditioning of the coal directly above the screw 9. A number of simple mechanical devices have heretofore been designed for shaking down the coal in the hopper, but my novel agitator is the only one found which I have found will in fact cause the screw 9 to feed a constant amount of powdered fuel from the hopper whether the hopper is full or nearly empty.

As shown in Figs. 1 and 3, the opposite side plates 1 of the hopper are connectecltcgether by metal straps ii, bolted or riveted to the plates; and secured to the centers of straps i l is a longitudinally disposed horizontal bar l2; and connected with the horizontal bar I2 adjacent the straps H are vertically disposed shaker bars I3 which extend downwardly with their lower ends terminating above and adjacent the screw shaft 8. Portions of the screw 9 are omitted in way of the lower ends of shaker bars 13, lugs i450 being provided on shaft 8, whereby as the shaft rotates the lugs :0 will strike the lower ends of shaker bars I3 and vibrate or jolt the hopper side plates 1, thereby positively shaking down the powdered fuel in the hopper into bottom 6 around screw 9. The above mentioned agitator l.l l2l3-I4 is essential in order to maintain the necessary even flow of coal required for efflcient operation of the apparatus, and same cannot be eliminated without impairing the operation to such extent that it may be rendered impractical.

At the outer end of casting 2, is a head casting which includes a duct l4 having a horizontal air inlet Ida, said duct curving downwardly over and around one side of casting 2 as shown in Fig. 1, with its outlet Mb disposed vertically and merging into a throat IS, the lower wall l5a of which is tangent to the casting 2 adjacent its bottom and slopes downwardly and laterally and terminates tangentially of a circular head 16 having a peripheral fiange lGa (Fig. 2) said head forming one end of a carburetor casing 37 disposed on a horizontal axis offset from and parallel with the shaftB. An opening lfib in flange [6a is provided in way of the throat l5 forming an inlet into head l6, and the walls of duct It at the outlet Mb merge into the walls of the throat l5 and the flange 16a. whereby the throat I5 is connected in an airtight manner to the head l6.

In the bottom of casting 2 adjacent the outer end of screw 9 is an opening 2b (Figs. 1 and 3) leading directly into'throat l5, and as shown in Figs. 2 and 3 the inner end 232 of bearing block 2a of casting 2 is cut in a plane disposed at such angle to the axis of shaft 8 that the coal, fed

the inner wall of outlet llb of duct Ml, said flap valve being of length sufficient to normally contact the bottom plate I5a of throat l5 when the valve is in vertical position shown in Fig. 1, in

which said valve substantially closes communication from opening 2b into the head It. An arm m on shaft l8, exterior to the throat, is

connected by a spring llb to a fixed lug I511: on

the exterior of the throat, said spring tending to normally maintain the flap valve I! closed.

A centrifugal blower l9, discharges air into the inlet- Ida of duct M, the blower taking in air around the shaft I90. of its impeller l9b and delivering same under pressure into the duct I l. A rubber, rubberized, or other elastic collar 20, secured by band 20a, connects the outlet of fan l9 with the inlet I40. of duct M.

Shaft Isa of blower I9 extends through an adjustable bearing 2|, and is preferably rotated by a belt 22 running over pulley 23 on fan shaft l9a and over a pulley 2% on the shaft 25a of the prim mover 25, preferably an electric motor, disposed coaxially of the head l6. Bearing 2l preferablycomprises a tubular body open at each end, and provided with ball bearings 2la for shaft ll9a. Body 2| is provided with a pedestal 2lb having anchor bolts 2 lo the heads of which engage elongated slots lm in base I, whereby when bolts Zlc are loosened the bearing 2| and the blower l9 which is supported thereon by clips I93: (Fig. 2) may be shifted as a unit towards or from the motor 25 to adjustthe tension of belt 22.

Mounted on fan shaft l9a is asecond belt pulley 26 opposite a pulley 21a on the driving shaft of a speed change mechanism 21 conventionally shown in Fig. 2, a drive belt 28 running around pulleys 26 and 21a. The driven shaft 21b of the speed change mechanism is axially aligned with screw shaft 8, and a coupling 81: connects shafts 8 and 21b, whereby the conveyor screw may be driven at various speeds from the blower shaft lBa.

The carburetor comprises a cylindrical casing 31 open at one end but having its perimeter at the open end offset as at 31a (Fig. 2) to fit within the peripheral flange l6a of head IS, the parts being secured together by any desired means, and said head I6 closing the open end of casing 31. plate 312) provided with an axially disposed outlet 3'lc adapted to be directly connected with the fuel burner (not shown). Within casing 31, axially thereof, is a shaft 28 connected directly with shaft 250. of motor 25, said shaft extending tlg ough a stuifing box 28a. in head l6.

On shaft 28, within the carburetor, are a plurality of stirrer blades 29 (four being shown) adapted to stir up the powdered fuel and to break up and thoroughly reduce any lumps or cakes of fuel, whereby the air within the carburetor may readily pick up the powdered fuel and pass the mixture of fuel and air directly into the outlet 31a and into the burner. The blades 29 are designed and arranged to give the greatest possible amount of turbulence, and are not in any way to be confused with fan blades, as the alternate blades 29 will actually act to retard the flow of air rather than assist same, and thus the coal and air is subjected to a thorough mixing due to the fact that the fuel and air have to work against the alternate whirling blades in passing through the carburetorto the outlet 310.

As shown in Figs. 1 and 2 each blade 29 com prises a flat plate having a narrow central portion provided with a hole to receive shaft 28 upon which same is mounted. Blades 29 are symmetri cal and fiare outwardly in width and have their outer portions crimped as at 29c, holes 29d being provided in the inner portions of the blades. Each of blades 29 is mounted on shaft 28 at such angle that the air current therefrom will be directed in the opposite direction from the adjacent blade, whereby the fuel and air mixture in the carburetor will be subjected to a thorough mixing in working towards outlet 31c.

Operation In operation, the prime mover 25 rotates blower shaft l9a, which shaft also rotates screw shaft 8 through'the speed reducing mechanism 21 to feed powdered coal from the hopper through casting 2 and into throat I5. The speed reducing mechanism 2'! may be set to regulate the amount of coal delivered to the air current in duct I, while rotating shaft B will simultaneously actuate the agitator lll2-l3 so that the pulverized or finely divided coal, or other solid fuel in the hopper is fed in a steady smooth or even stream into the throat regardless of whether the hopper is full or is nearly empty, since the coal will be vibrated by the agitator not only directly fiufiiness in the coal at this point, but the sides I of the hopper will also be vibrated to cause any coal in the hopper to slide down properly, eliminating tunnelling of the coal around screw 9.

The screw 9 feeds the coal into throat l5 against the light but steady pressure of, the spring loaded flap valve I! which tends to discharge the coal into the air currents in the throat in a smooth steady'stream. Beyond flap valve I! the coal is picked up by the air currents and carried into the carburetor 31 where the powdered coal will be thoroughly mixed with and carried over by the air through the outlet 31c directly to the burner (not shown), the rapidlyv rotating blades 29 insuring that all lumps or adhering particles of coal will be reduced as said blades are arranged to give the greatest possible amount of turbulence. The coal and air fuel mixture is taken off the back 311) of the car- The opposite end of casing?! is closed byover and around the screw 9, creating a uniform buretor 31 at the axis of the mixing blades 28.

I claim:

1. In apparatus of the character specified, a housing for powdered material having an outlet; means including a screw shaft in the housing to convey the material to said outlet; a carburetor casing having an inlet and outlet; an air duct extending adjacent the housing outlet and into the carburetor inlet; an offset throat in said duct communicating with the housing outlet; means for forcing air under pressure into said duct; a yieldable flap in said throat at the housing outlet; the housing outlet being disposed above and to one side of the carburetor inlet; and said air duct having a bottom wall sloping downwardly from the housing outlet to the carburetor inlet and substantially tangent to the carburetor cas- 2. In apparatus of the character specified, a housing for powdered material having an outlet;

means including a screw shaft in the housing to convey the material to said outlet; a carburetor casing having an inlet and outlet; an air duct extending adjacent the housing outlet and into the carburetor inlet; an offset throat in said duct communicating with the housing outlet; means for forcing air under pressure into said duct; a yieldable flap in said throat at the housing out let; the housing outlet being disposed above and to one side of the carburetor inlet; said air duct having its bottom wall sloping downwardlyfrom the housing outlet to the carburetor inlet and substantially tangent to the carburetor casing; said carburetor being cylindrical; an axially disposed shaft in said carburetor; a series of radial blades on said shaft; and means for rotating the shaft to move the blades in a direction opposite to that of the air and coal entering the inlet.

3. In apparatus of the character specified: a housing having an outlet; means including a screw shaft for conveying material through the housing to said outlet; a carburetor having a tangential inlet and an axial outlet; the housing outlet being disposed above and to one side of the carburetor inlet; an air duct extending adjacent the housing outlet and into the carburetor inlet, the bottom wall of said duct sloping downwardly from the housing outlet to the carburetor inlet; an offset throat in said duct communicating with the housing outlet; a yieldable flap valve in said throat at the housing outlet; and means for forcing air into the air duct.

4. An apparatus as set forth in claim 3; said carburetor being cylindrical; an axially. disposed shaft in said carburetor; a series of radial blades on said shaft; and means for rotating the shaft .at the other end; an axially disposed shaft in said carburetor; and a series of flat blades on said shaft arranged at angles to the axis of the shaft, adjacent blades of the series being inclined so. as to produce air currents in opposite directions, whereby a maximum turbulence will be produced within the carburetor between the inlet and outlet.

6. In apparatus of the character specified; a housing having an outlet; means including a screw shaft for conveying material through said housing to said outlet; a carburetor adjacent the housing having a tangential inlet and an axial outlet; an air duct extending adjacent the housing outlet and into the carburetor inlet; an offset throat in said duct communicating with the housing outlet; means for forcing air under pressure into said air duct; a yieldable flap valve in said throat at the housing oitlet; said carburetor being cylindrical; an axially disposed shaft in said carburetor; and a series of flat blades on said shaft arranged at angles to the axis of the shaft, adjacent blades of the series being directed to produce air currents in opposite directions, whereby a maximum turbulence will be produced within the carburetor between the inlet and outlet; and the inlet and outlet being disposed at opposite ends respectively of theseries of blades.

7. In apparatus as set forth in claim 6, said blades being of narrow width at their hub portions and wideningtowards their outer ends, the outer portions of the blades being crimped.

8. An apparatuses set forth in claim 6, the housing outlet being disposed above and to one side of the carburetor inlet; and said air duct having a bottom wall sloping downwardly from the housing outlet to the carburetor inlet and substantially tangent to the carburetor casing.

9. An apparatus as set forth in claim 6, the

housing outlet being disposed above and to one .side of the carburetor inlet; said air duct having on said shaft; and means for rotating the shaft W'HLIAM B. ROGERS. 

